Nanoimprint technology is a development advanced from embossing technology well known in the art of optical disc production, which comprises pressing a mold original with an embossed pattern formed on its surface (this is generally referred to as “mold”, “stamper” or “template”) against a resin to thereby accurately transfer the micropattern onto the resin through mechanical deformation of the resin. In this, when a mold is once prepared, then microstructures such as nanostructures can be repeatedly molded, and therefore, this is economical, and in addition, harmful wastes and discharges from this nanotechnology are reduced. Accordingly these days, this is expected to be applicable to various technical fields.
Two methods of nanoimprint technology have been proposed; one is a thermal nanoimprint method using a thermoplastic resin as the material to be worked (for example, see S. Chou, et al., Appl. Phys. Lett. Vol. 67, 3114 (1995)), and the other is a photonanoimprint method using a photocurable composition (for example, see M. Colbun, at al., Proc. SPIE, Vol. 3676, 379 (1999)). In the thermal nanoimprint method, a mold is pressed against a polymer resin heated up to a temperature higher than the glass transition temperature thereof, then the resin is cooled and thereafter released from the mold to thereby transfer the microstructure of the mold onto the resin on a substrate. The method is applicable to various resin materials and glass materials and is expected to be applicable to various fields.
On the other hand, in the photonanoimprint method where a photo-curable composition is cured by photoirradiation through a transparent mold or a transparent substrate, the transferring material does not require heating in pressing it against the mold, and therefore the method enables room-temperature imprinting. Recently, new developments having the advantages of the above two as combined, have been reported, including a nanocasting method and a reversal imprint method for forming three-dimensional structures.
For the nanoimprint methods as above, proposed are applied technologies mentioned below.
In the first technology, the molded pattern itself has a function, and is applied to various elements in nanotechnology and to structural members. Its examples include various micro/nano optical elements and high-density recording media, as well as structural members in optical films, flat panel displays, etc.
The second technology is for hybrid-molding of microstructures and nanostructures, or for construction of laminate structures through simple interlayer positioning, and this is applied to production of μ-TAS (micro-total analysis system) and biochips. In the third technology, the formed pattern is used as a mask and is applied to a method of processing a substrate through etching or the like.
In these technologies, high-precision positioning is combined with high-density integration; and in place of conventional lithography technology, these technologies are being applied to production of high-density semiconductor integrated circuits and transistors in liquid-crystal displays, and also to magnetic processing for next-generation hard discs referred to as patterned media. Recently, the action on industrialization of the above-mentioned nanoimprint technologies and their applied technologies has become active for practical use thereof.
As activities regarding the photonanoimprint method have increased, an issue of adhesiveness between a substrate and a curable composition for imprints has been gaining more attention. In more details, the curable composition for imprints is generally applied to the surface of the substrate to form a layer, and is cured by photoirradiation while being kept under a mold, but the curable composition for imprints may adhere onto the mold when the mold is separated thereafter. Poor separability of the mold may degrade formability of the resultant patterns. This is ascribable to a part of the curable composition for imprints remaining on the mold.
It has therefore been demanded to improve adhesiveness between the substrate and the curable composition for imprints. Known techniques for enhancing the adhesiveness between the substrate and the curable composition for imprints are disclosed in R. S. Williams et al., Langmuir 21, 6127 (2005), Houle et al., J. Vac. Sci. Technol., B 25(4), 1179 (2007), and Published Japanese Translation of PCT International Publication for Patent Application Nos. 2009-503139 and 2011-508680. More specifically, according to R. S. Williams et al., Langmuir 21, 6127 (2005), Houle et al., J. Vac. Sci. Technol., B 25(4), 1179 (2007), and Published Japanese Translation of PCT International Publication for Patent Application Nos. 2009-503139, the adhesiveness between the substrate and the curable composition for imprints is improved by using a polymerizable compound having a group interactive with the substrate. On the other hand, according to Published Japanese Translation of PCT International Publication for Patent Application Nos. 2009-503139 and 2009-503139, the adhesiveness between the substrate and the curable composition for imprints is improved by using an addition condensation polymer having a polymerizable group.